21789540 has 48 divisors (see below), whose sum is σ = 67791360. Its totient is φ = 5810400.

The previous prime is 21789511. The next prime is 21789557. The reversal of 21789540 is 4598712.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21789495 and 21789504.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19636 + ... + 20715.

It is an arithmetic number, because the mean of its divisors is an integer number (1412320).

Almost surely, 2^21789540 is an apocalyptic number.

21789540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21789540 is an abundant number, since it is smaller than the sum of its proper divisors (46001820).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21789540 is a wasteful number, since it uses less digits than its factorization.

21789540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40369 (or 40361 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21789540 is about 4667.9267346436. The cubic root of 21789540 is about 279.3075577036.

The spelling of 21789540 in words is "twenty-one million, seven hundred eighty-nine thousand, five hundred forty".